Conventionally, an axle driving apparatus, which vertically divides a casing thereof and journals axles at the divided surfaces and drives the axles by a hydro-static-transmission attached to the casing, is well known as disclosed in, for example, the Japanese Utility Model Publication Gazette No. Sho 62-44198 and the Japanese Patent Laid-Open Gazette Sho 62-101945, filed by the same applicant.
In the conventional prior art, however, the hydro-static-transmission separate from the axle driving apparatus is fixed to the outside thereof in a manner of being exposed, whereby the apparatus is large-sized as a whole and larger in the gross weight. Also, it is required for driving the horizontally disposed axles by a motor shaft of a hydraulic motor vertically disposed at the exterior to interpose bevel gears in a drive system for both the motor shaft and axles.